Sir; Michael Brown ("Will Tony Benn find himself in one of Straw's gulags?", 16 February) unthinkingly censures the Liberal Democrats for not offering blanket opposition to Jack Straw's proposals for the detention of psychopaths.

Liberalism is not a belief that "anything goes"; it is a belief in liberty in things wherein we do no harm to others. The right of the public to protection against murder, arson and rape is as much a liberty as the need to prevent wrongful detention.

What is wrong about Jack Straw's proposals is that they are being introduced by the wrong government department. The use of criminal law to punish people for offences they have not yet committed is indeed a dangerous precedent. The detention of psychopaths, as Michael Stone seems to have dimly realised, must be justified for the protection of the potential offender as well as that of the public. That means the appropriate department is the Department of Health, although no treatment is involved.

When the Liberal Democrats put up our health spokesman and not our home affairs spokesman to discuss these proposals we were going in the right direction. If we further point out that liberalism does not offer cheap, easy answers to problems which may be insoluble we are telling the truth.